High-frequency oscillator



1, 1949. w", HQTlNE 2,462,866 HIGH-FREQUENCY OSCILLATOR Filed Nov. 30,1942 NEWER A vvvvvvvvvv.

y INVENTOR.

WILL/#M HOT/NE Patented Mar. 1, 1949 itineranti nuora UNITED STATESPATENT OFFICE Federal Telephone and Radio Corporation,

Newark, N. J., a corporation of Delaware Application November 30, 1942,Serial No. 467,375

(Cl. Z50- 36) 1 Claim.

rIhis invention relates to improvements in high frequency oscillators,and more particularly to vacuum tube oscillators adapted to operate atultra-high frequencies.

An object of this invention is the construction of a high frequencyvacuum tube line oscillator which will operate at higher frequencieswith standard type tubes than heretofore possible.

Another object of this invention is to provide a new and improved highfrequency line oscillator `of the type adapted to receive standard typesof vacuum tubes as part of a constructional unit.

A further object of this invention is to provide a high frequency vacuumtube line oscillator of the grounded grid type, in which couplingbetween the plate and cathode lines is eiected by the inductivereactance of a common grid condenser.

A still further object of this invention is the provision of a highfrequency oscillator in a novel construction forming such plate andcathode lines together with the common grid condenser as a structuralunit.

Other objects and advantages of the present invention will appear tothose skilled in this art from the following description of a preferredembodiment thereof, illustrated in the accompanying drawings, wherein:

Fig. 1 is a longitudinal cross-sectional view of a preferred form ofoscillator constructed in accordance with the present invention; and

Fig. 2 is a circuit diagram of the oscillator illustrated in Fig. l.

As appear in the drawings, the oscillator comprises a first coaxial lineIl) formed of an outer metal cylinder I2 and an inner metal rod I4, anda second coaxial line I6 consisting of an outer metal cylinder I8 and aninner metal cylinder 2l). The two lines I and I6 are connected togetheras a structural unit through a suitable ringshaped member 22 connectedon one hand to the outer metal cylinder I 2 of the coaxial line I0, andon the other hand to the outer metal cylinder I8 of the coaxial line I6.

The outer co-planar ends of the cylinder I8 and forming the coaxial lineI6 are preferably electrically interconnected as indicated at 23. Theinner end of the metal cylinder 20 is provided with suitable springmembers 24, which may extend about and grip the metal shell 26 of aninserted vacuum tube 28. The cathode line I6 may be tuned by theprovision of a longitudinally adjustable short-circuiting ring 3l),which may be moved from without the oscillator by any suitable means(not shown).

Adjacent the ring-shaped member 22 connecting the outer metal cylindersI2 and I8 I place a ring 32 of insulating material adapted to support ametal disk 34 having a central opening provided with circumferentiallyspaced spring iingers 36 so positioned relatively to the vacuum tube 38as to grip and contact a grid lead in the form of metal ring 38. Thejuxtaposed surfaces of the ring-shaped member 22 and the metal disk 34,insulated therefrom, are so designed as to form between them a condenser39. Thiscondnser may be shunted by a suitable grid resistor 4 The vacuumtube 28 is preferably of the type having an anode cap 42 on the end ofthe tube opposite the metal shell 26, and the anode Cap 42 is adapted tobe gripped and contacted by suitable spring fingers 44 attached to theinner end of the rod I4. The outer end of the rod I4 is preferablyco-planar with the outer end of its surrounding metal cylinder I2, andis supported relatively to the latter by a suitable insulator 46.Connection for alternating current voltages between the rod I4, whichmay form the high voltage anode lead, with the outer cylinder I2formingr the plate line, may be accomplished through a blockingcondenser 41. In the preferred form of invention illustrated, thecondenser 41 is formed as a slidably mounted unit between rod I 4 andmetal cylinder I2, consisting of an outer metallic ring 48 contactingthe inner surface of the cylinder I2, and an inner metal ring 50contacting the outer surface of the rod I4, separated by a ring ofinsulation 52. As will be clear to those skilled in this art, thecoaxial line I0 may be tuned by varying the position of the condenser 41in one direction or the other, and this movement may be controlled byvarious means well known to the art (not shown).

Extending from the base of the tube 28 I have indicated the cathode lead54, theheater leads 56 and 60, and another lead '58 which is connectedto the metal shell 26. The leads 54, 5B and 58 may be interconnected bysuitable jumpers as illustrated, the heater potential then beingconnected across the leads 54 and 60, the lead 54 also being connectedto the negative side of the high potential source.

The construction described above permits oscillations to be generated byproviding means for impressing voltage of the proper phase and sufcientamplitude on grid G of tube 28. The schematic circuit diagram of Fig. 2shows the electrical circuit. The plate to grid circuit includes Cep,the variable plate line I8, blocking condenser 41, condenser 39 withshunt resistor 40, and inductance 34 of the metal disc contacting theannular grid lead. The plate line I is tuned to less than a quarter-wavelength at the operating frequency, so that it appears as an inductivereactor, and is shown in dotted lines as an inductor. The cathode togrid circuit includes Cgk, variable cathode line I6, condenser 39 withshunt resistor 40, and inductor 34. The cathode line I6 is tuned to morethan a quarter wave length and less than one-half wave length at theoperating frequency, so that it appears as a condensive reactor, and isshown in dotted lines as a capacitor. The plate to cathode circuitincludes Cpk, plate line I0, and cathode line I6. An intermediate pointbetween the coaxial line outer conductors may be grounded as indicated,and a suitable high voltage may be applied to anode P by a connectionbetween ground and rod I4.

When using coaxial lines for cathode and plate circuits with the gridconnected at the intermediate point of these lines, as is well known tothe art in using the triode type of tube with annular grid lead out as agrounded grid, or inverted amplifier, the small effective plate tocathode capacity may be insuicient to produce oscillations.

The present invention provides means for impressing suflicient feedbackvoltage on the grid to produce oscillation by inserting the effectiveinductor 34 in series with the low inductance annular grid lead out. Themechanical arrangement of inductor 34 is made so that electrically, itis common to both plate to grid, and cathode to grid, circuits. Themechanical size of inductor 34 is designed so that its electricalinductance is of the proper magnitude at the operating frequency. In theoscillator shown, inductor 34 is also utilized as one plate of acondenser. Other mechanical arrangements may be made, as can readily beseen by those versed in the art, in which inductor 34 may take othersuitable mechanical forms, while satisfying the electrical requirementsstated above.

The constructional unit illustrated in Fig. 1 has been particularlydesigned for use with a vacuum tube of the type known to the art as G.E. Z. P. 446, although it is to be made clear that the principles of thepresent invention and the structural unit itself are applicable to othertypes of tubes which are operable at high frequencies. Slight structuralmodifications may be necessary in the event that other tubes are used,but it is considered that any modications necessary would be whollywithin the skill of those working in this art.

Accordingly, while I have described above the principles of my inventionin connection with certain specific apparatus, it is to be clearlyunderstood that this description is made only by way of example and notas a limitation on the scope of my invention as set forth in the objectsand the accompanying claim.

I claim:

A high frequency oscillator comprising in combination agpti*rmof coaxialtransmission lines, means for coupling the outer conductors of eachline, an electron discharge device having a metal shell section at oneend thereof connected to its cathode, an anode connector projecting fromthe other end, andamingshaped gridrconnector betweenwitsends, means formounting said Ydevice within said coaxial lines including members on oneend. of the inner conductor of one coaxial line gripping said metalshell and other members on one end of the inner conductor of the othercoaxial line gripping said anode connector, a metal disc having anopening at its center surrounding and gripping said grid connector,means for insulatingly supporting the periphery of said metal disc fromsaid outer conductors substantially at their common connecting point,said inner conductor of the other coaxial line' being in the form of asolid rod, and means for insulatingly supporting the outer end of saidrod within the outer end of its surrounding conductor in combinationwith an integral slidable ring-shaped member positioned between andcontacting said inner and outer conductors, said ring-shaped memberincluding an outer metallic ring contacting the inner surface of theouter conductor, an innermetallic ring contacting the outer surface ofthe inner conductor, and a nar row band of insulationseparating said tworings.

' WILLIAM HOTINE.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 2,408,355 Turner Sept. 24, 19462,411,424 Gurewitsch Nov. 19, 1946

